It is desirable to collect a variety of biological fluids for later use or testing. In particular whole blood or blood components are often collected for later use in patients. Blood or blood components are often collected from the donor in a collection bag. It is recommended that the blood be collected in a sterile fashion and have an anticoagulant and/or preservation solution added at the time of collection so as to allow its subsequent use and the best sanitary safety conditions. Prior to collection, the collection bag is normally filled with the anticoagulant and/or preservation solution.
One of the problems posed by inclusion of an anticoagulant and/or preservation solution in the collection bag is that, in order to produce a homogeneous mixture of the fluid and the solution contained in the bag, it is necessary to agitate the collection bag, which complicates the collection process and does not ensure a proper mixture.
Another problem concerns obtaining a given ratio between the quantity of fluid collected and the quantity of anticoagulant and/or preservation solution added. This problem occurs because, particularly when collecting blood, the quantity of anticoagulant and/or preservation solution present in the collection bag is fixed at a certain value so that the blood can be used in the medical field. When the anticoagulant and/or preservation solution is present in the collection bag prior to collecting the fluid, the ratio of solution to fluid is correct only for a given quantity of fluid collected. Additionally, this ratio of solution to fluid is considerably higher at the start of fluid collection or if collection is interrupted before the entire quantity of fluid required is collected. In the case of blood, this may result in a reduction of the quality of the blood by lysis of the red corpuscles and deterioration of the functionality of the platelets. The blood collected may deteriorate to the point where it becomes unusable.
To solve this problem, it has been proposed, in particular in FR 2,808,693 and U.S. Pat. No. 6,113,554, to place the anticoagulant and/or preservation solution in a bag separate from the collection bag and to supply the collection bag with solution simultaneously during collection of the fluid. These approaches do not sufficiently solve the problem, however.
First, a problem persists concerning obtaining a proper ratio between the quantity of fluid collected and the quantity of anticoagulant and/or preservation solution added. The ratio is obtained either by using a specific bag system or by using a complex pump structure, which complicates use and substantially increases the cost of fluid collection.
Second, another problem persists relating to pumping the fluid which, by imposing a flow on the fluid collected, is necessary for obtaining the desired ratio in previous systems. For safety reasons and when collecting blood from a donor, it is then desirable to use a pressure sensor for the fluid upstream of the pump in order to prevent any risk of collapse of the donor's vein. This sensor, apart from its complexity and cost, may give rise to problems of asepsis if it is based on a gaseous exchange between the inside and outside of the collection system. In addition, the pumping is a source of discomfort and insecurity for the donor.